Modern automobile engines typically are compactly enclosed within engine compartments that are poorly ventilated when the engine is inoperative. Consequently, cooling the engine and the air around the engine with the engine compartment becomes ever more difficult and average temperatures therein have increased with each new model car. Resultantly, high engine compartment temperatures increase the difficulty in restarting an engine after a sustained hot soak period. The hot soak refers to the period of time during which a heated engine is de-energized and, thus, the cooling fans and other engine cooling components are also de-energized. The result is a greatly increased engine compartment temperature. Upon attempting to restart the engine, fuel entering the abnormally hot engine carburetor tends to foam or percolate, which action grossly affects the fuel-air ratio of the engine. In fact, the foaming of the fuel in the carburetor often causes the fuel-air ratio to be too rich for engine starting.
This problem of fuel foaming in the carburetor subsequent to a hot soak is discussed in SAE Paper 821202 entitled "Carburetor Foaming and Its Influence On The Hot Weather Performance of Motor Vehicles." The authors are V. M. Tertois and B. D. Caddock of Shell Research Limited. Two hot fuel handling problems are discussed in the paper and are often confused with one another. One, and the most well known problem, is that of vapor lock in the fuel pump. Vapor lock results from excessive vapor generation due to overheating of the pump. Vapor lock inhibits the replenishment of liquid fuel in the carburetor bowl and will cause engine starving. Vaporization of the light hydrocarbons are a primary cause of vapor lock. Many patents relate to devices for preventing vapor lock and some are listed hereafter.
The second, but less well known, hot fuel handling problem results when fuel foams in a hot carburetor. Normally, this foaming of fuel occurs after a hot soak period in which engine compartment temperatures are increased substantially above normal. When fuel is pumped from a relatively cool fuel tank and into an abnormally hot carburetor, gasoline foams and will tend to block the carburetor bowl vent. This causes fuel to flow through the carburetor and into the throttle bore in an unmetered and undesirable fashion. The result is an overly rich fuel-air mixture which may prevent restarting of the engine after the hot soak. Various suggestions are made to solve this problem in the SAE Paper 821202, none of which are totally satisfactory in most circumstances.
The subject application discloses a simple fuel conditioning device which provides for a significant quantity of fuel to be exposed to the hot test location in the engine compartment. The device is located in the hottest portion of the engine compartment which is just beneath the engine hood and near the carburetor. Upon restarting an engine after a hot soak, the heat conditioned fuel in the fuel conditioning device flows into a relatively hot carburetor, but the fuel will not percolate or foam as would relatively cool fuel which flows into a hot carburetor. The quantity of fuel in the fuel conditioning device is sufficient to start the engine and operate it for a sufficent time after a hot soak to evacuate hot air from the engine compartment primarily by use of the engine fan.
Consequently, an object of the present invention is to provide a fuel conditioning device and system for vehicle engines which will temperature condition a quantity of fuel sufficiently to start and run the engine after a prolonged hot soak period.
A further object of the present invention is to provide a fuel conditioning device and system for a vehicle engine within a relatively confined engine compartment thereby subject to large temperature increases during a hot soak period of engine inactivity, the fuel conditioning device and system including a heat conductive fuel reservoir adjacent the carburetor and located in the uppermost and hottest part of the engine compartment to provide a supply of high temperature fuel to flow into a relatively hot carburetor upon restart after the hot soak period.